1. Field of the Invention
The present invention relates to surface coatings, and, more particularly, to such coatings for use in or on an aqueous environment or in contact with an aqueous fluid or solid.
2. Description of Related Art
Coatings for application to structures in or on aqueous environments and static underwater structures are known for use to preserve surfaces, improve their appearance, and reduce drag for moving structures or devices. Such structures or devices may comprise, but are not intended to be limited to, movable boats such as sailboats, yachts, inboard and outboard motor boats, rowboats, motor launches, canoes, kayaks, inflatable watercraft, waterskis, snow skis, jetskis, snowboards, snowmobiles, toboggans, bobsleds, surfboards, sailboards, waterbikes, ocean liners, tugboats, tankers, cargo ships, submarines, aircraft carriers, pontoons for sea planes, and destroyers. Underwater static structures may include, but are not intended to be limited to, wharves, piers, pilings, bridges, and other structures that may comprise wood, metal, plastic, fiberglass, glass, or concrete.
Some coatings known in the art include those described in U.S. Pat. Nos. 3,575,123; 4,100,309; 4,119,094; 4,373,009; 4,642,267; 5,488,076; 5,554,214; and 5,700,559. Antifouling compositions have also been known to be used against such organisms as barnacles, algae, slime, acorn shells (Balanidae), goose mussels (Lepodoids), tubeworms, sea moss, oysters, brozoans, and tunicates (e.g., U.S. Pat. No. 5,919,689).
Coatings may be hydrophilic or hydrophobic, the latter incurring friction between the moving surface and the water and including Teflon-like, paraffin wax, and fluorocarbon/silicone materials. The former maintains an adhering layer of water, the kinematic friction occurring with the water through which the craft moves.
It is therefore an object of the present invention to provide a method of reducing kinematic friction between a watercraft or water-contacting surface and the water through which the watercraft moves.
It is an additional object to provide a coating for a watercraft for reducing kinematic friction.
It is a further object to provide such a coating that is hydrophilic.
It is another object to provide such a coating that also possesses antifouling properties.
It is yet an additional object to provide a new use for a novolak-type polymeric composition.
An additional object is to provide a composition and method for improving fuel efficiency in watercraft.
A further object is to provide a composition and method for coating a surface intended to contact water in either a liquid or frozen state to improve kinematic friction.
Another object is to provide a composition and method for coating a surface to reduce noise associated with contact with water.
It is an additional object to provide a composition and method for coating a surface to absorb shock associated with water and wave contact.
It is a further object to provide a composition and method for coating a surface to protect against corrosion and/or blistering.
These objects and others are attained by the present invention, a composition and method for coating water-contacting surfaces having the property of reducing kinematic friction. It is to be understood by one of skill in the art that by xe2x80x9cwaterxe2x80x9d is meant any aqueous environment, freshwater or marine, as well as in a frozen state, i.e., ice or snow. An embodiment of the composition comprises a solution including a polymer comprising a polyhydroxystyrene of the novolak type. The polymer may be present in a concentration range of trace to the solubility limit, approximately 75% in alcohol. In a preferred embodiment the composition further comprises an antifouling agent.
In a first subembodiment of the composition, the polyhydroxystyrene is blended in a low-molecular-weight oxygenated hydrocarbon solvent. In a second subembodiment, the polyhydroxystyrene is incorporated into a gel-type coating. In a third subembodiment, the polyhydroxystyrene is incorporated into an epoxy, such as a one- or a two-part epoxy, for forming a permanent or semipermanent coating.
A first embodiment of the method of the present invention comprises applying the composition as described above to an outer surface of a marine watercraft or to any water-contacting surface to achieve a coating thereof. Preferably the composition is applied in a solution in an appropriate solvent, which may comprise a low-molecular-weight oxygenated hydrocarbon such as an alcohol or ketone. The coated surface is smooth and free of tackiness and thus is not fouled by common water debris such as sand and weeds. The coating is insoluble in water and resists abrasion, giving a functional lifetime that has been estimated to be a few years of continuous use.
A second embodiment comprises a method for increasing the kinematic efficiency of a marine watercraft, including applying the composition to a submersible surface of a marine watercraft.
A third embodiment comprises a method for making the composition, including blending the polyhydroxystyrene in a low-molecular-weight oxygenated hydrocarbon solvent, a gel coat, or an epoxy.
A fourth embodiment comprises a method for reducing noise of water and wave impact, including applying the composition to a water-contacting surface such as a roof.
A fifth embodiment comprises a method for absorbing shock experienced by water-contacting surfaces, such as boat hulls, including applying the composition thereto.
A sixth embodiment comprises a method for protecting a water-contacting surface from corrosion or blistering, including applying the composition to the affected surface.
An application of the composition of the present invention to a water-submersible surface results in a hydrophilic surface having a considerably reduced contact angle. For example, when the composition is applied to a fiberglass/polyester surface with an initial contact angle of approximately 60xc2x0 with water as determined by the tilting plate method (see N. K. Adam, The Physics and Chemistry of Surfaces, Oxford Univ. Press, 1941), the contact angle is reduced to about 15xc2x0. Thus the use of the coating is beneficial on watercraft to increase the speed thereof and/or to improve the fuel utilization.
The features that characterize the invention, both as to organization and method of operation, together with further objects and advantages thereof, will be better understood from the following description used in conjunction with the accompanying drawing. It is to be expressly understood that the drawing is for the purpose of illustration and description and is not intended as a definition of the limits of the invention. These and other objects attained, and advantages offered, by the present invention will become more fully apparent as the description that now follows is read in conjunction with the accompanying drawing.